Novel fluoropyrimidine-based chemotherapy for advanced well-differentiated neuroendocrine tumors: a clinical update.

Introduction: Patients with advanced well-differentiated neuroendocrine tumors (NETs) who have bulky and/or symptomatic and/or rapidly progressive disease require chemotherapy treatment.Areas covered: This review summarizes the accumulating evidence for treatment with fluorouracil-based chemotherapy in well-differentiated NETs. The main clinical studies, toxicity and predictors of fluorouracil- based chemotherapy regimens in well-differentiated NETs are discussed, along with the current issues, future research directions and therapeutic prospects.Expert opinion: Somatostatin analogs may control symptoms of hormone excess and tumor growth in patients with well-differentiated metastatic NETs, and biological therapies may improve progression-free survival for these patients. However, chemotherapy leads to higher objective response rates and symptom control by reducing tumor bulk. The low response rate and significant toxicities of conventional chemotherapy regimens limit their widespread use. Fortunately, some novel fluoropyrimidine-based treatment including fluorouracil, capecitabine, or S-1 based chemotherapy with or without antiangiogenic agents have been investigated in recent years. These treatments showed significant efficacy and less toxicity in pancreatic and non-pancreatic metastatic well-differentiated NETs. Additionally, non-pancreatic well-differentiated NETs have also achieved similar tumor response or survival comparable to pancreatic NETs. Moreover, some predictors of response to these treatment regimens have been evaluated.